Figure 280. Center-Aligned Pwm Waveforms (Arr=8) - ST STM32L4x6 Reference Manual

General-purpose timers (TIM2/TIM3/TIM4/TIM5)
Hints on using center-aligned mode:
•
When starting in center-aligned mode, the current up-down configuration is used. It
means that the counter counts up or down depending on the value written in the DIR bit
in the TIMx_CR1 register. Moreover, the DIR and CMS bits must not be changed at the
same time by the software.
•
Writing to the counter while running in center-aligned mode is not recommended as it
can lead to unexpected results. In particular:
–
–
•
The safest way to use center-aligned mode is to generate an update by software
(setting the UG bit in the TIMx_EGR register) just before starting the counter and not to
write the counter while it is running.
884/1693

Figure 280. Center-aligned PWM waveforms (ARR=8)

The direction is not updated if you write a value in the counter that is greater than
the auto-reload value (TIMx_CNT>TIMx_ARR). For example, if the counter was
counting up, it continues to count up.
The direction is updated if you write 0 or write the TIMx_ARR value in the counter
but no Update Event UEV is generated.
DocID024597 Rev 3
RM0351